FLashing firmware on SIPY not working

We are building the firmware from GIT (usingmake etc.). For LopY and GPY everything is running fine but not for SIPY.
The firmware is flashed but the modem pac is always b'\xff\xff\xff\xff\xff\xff\xff\xff'

With your last pycom tool updater (1.15.1) we can not update SIPY... the tool dialog show message "paste pybytes token".